1. Field of the Invention
This invention relates to a camera arranged to be capable of varying the amount of flash light emission.
2. Description of the Related Art
It has been known to arrange a flash device to accumulate electric energy in a main capacitor to a given capacity level by boosting the voltage of a battery which is provided as a power source for a camera and then to excite and allow a xenon lamp to flash at a given timing. The use of the flash device effectively prevents an object to be photographed from becoming too dark in a dark scene or under a back light condition.
An improvement over the flash device which is also known is arranged to measure the reflected light of the object resulting from flashing and to stop the flash device from flashing when the reflected light reaches a predetermined value of light quantity on an image plane. This arrangement is called a flash light control device. The use of the flash light control device broadens a flash device interlocking range (by preventing an over-exposure for a near distance). It also saves any nearby person from being dazzled too much. This device is widely in use for single-lens reflex cameras on account of these merits.
Meanwhile, cameras of the kind having a distance measuring device for automatically measuring a distance to the object have recently increased in number. The cameras of the kind arranged to be capable of varying their focal lengths and also the cameras of the kind having a flash device of a high guide number also have increased.
However, the use of the above-stated flash light control device for these cameras necessitates an optical system and an electric circuit for measuring reflected light at the time of flashing and also means for actually fitting them, and thus has presented a problem in respect of space and cost. This problem is not only serious for single-lens reflex cameras but especially serious for low-priced, lens-shutter type cameras having various functions, because of lack of space or limited cost.
Another problem lies in that the flash light control on the basis of reflected light of the object resulting from flashing depends on the reflection factor of the object and also those of ambient things. It has been, therefore, sometimes difficult to make an apposite exposure. In accordance with the conventional flash light control method, the photographed face of a person, for example, often becomes darker in a case where he or she is in front of a golden background, and sometimes becomes blankly white when he or she is in front of a background which is blackish as a whole.
Further, in accordance with the arrangement of the conventional flash light control device, the photoelectric current obtainable from the reflected light of the object is very weak. Therefore, the flash light quantity sometimes becomes greatly insufficient through the flash light control due to some flashing noise or the like. To prevent this, the conventional flash light control device necessitates a great amount of efforts and parts for actual applications. Further, the value of light quantity on the image plane becomes unreliable when some dust or a waterdrop sticks to an optical system for flash light control or when shots are taken in the rain.
A further problem with the conventional device lies in that: Although the flash light is not extremely dazzling, it is still dangerous for children's eyes to flash at them from a short distance. In view of this, some people wish to take a picture with the guide number of the flash device lowered. There is another desire to vary the ratio of the flash light to daylight under some distance condition in connection with wide-field distance measurement. There is also a desire for taking a near distance shot while increasing the depth of field.